1. Field of the Invention
The present invention relates to apparatus for conveying hot glass sheets in a non-vertical orientation and particularly relates to apparatus for conveying hot, shaped glass sheets through a glass sheet chilling station, although the apparatus is also adapted to convey hot, flat glass sheets through the cooling station.
The rolls of the present invention are particularly adapted for use in a roller conveyor. When glass sheets are bent and then cooled for tempering or heat strengthening, the glass is first heated to its deformation temperature so that it can be shaped into the desired curvature. However, when glass sheets are sufficiently hot to be shaped or heat strengthened, the glass surfaces are very susceptible to becoming marked and/or distorted, especially when the hot glass is conveyed along a series of rotating conveyor rolls having sufficient rigidity at elevated temperatures needed for glass tempering to support and propel the glass sheets through regions of different temperatures.
It has been suggested to selectively chill the surface only of the hot glass sheets to reduce surface markings caused by direct contact of the rotating roll against the heat-softened glass sheet surfaces. However, any premature chilling of the glass surface reduces the overall glass temperature and reduces the maximum compression stress that can be obtained by subsequent chilling. Furthermore, any chilling that is uneven from surface to surface may cause warpage of the sheet and it is difficult to obtain a cooling pattern symmetrical about the center of the glass thickness that avoids warpage.
It has also been proposed to shape the glass like a dome and support the glass along its longitudinal side edges only from the shaping station to the chilling station in order to reduce glass to roll contact during the time the glass sheet is hot enough to be readily distorted or marked. If the shaped glass is deposited directly on the conveyor rolls, the utility of such a suggestion is limited to certain shapes of glass having straight side edges only.
Carriages with movable glass supporting fingers have been used to transport glass sheets from a shaping station for deposition onto rotating conveyor rolls at a chilling station. Such finger supports may sometimes provide too small an area for supporting the entire glass mass and may thus cause local variations from desired shapes or dimpled regions that result in optical distortion when the glass is too heavy to be supported on spaced fingers defining narrow areas of support.
Flat glass sheets have been supported on solid conveyor rolls provided with covers of a material that does not harm glass on rolling contact therewith. However, prior to the present invention, conveyor rolls provided with capability of adjustment to curved shapes to conform to the shape of conveyed glass sheets were not capable of rapid adjustment when it was required to change the apparatus for treating glass sheets to adapt the apparatus for a different pattern having a different shape from one previously produced. Furthermore, no glass conveying apparatus provided with fulid permeable rolls was available prior to the present invention that altered the shape of each conveyor roll to approximately the exact supporting shape of each other roll in the portion of the conveyor system for moving glass sheets through a glass chilling station.
2. The Prior Art
U.S. Pat. No. 3,807,546 to Canonaco and U.S. Pat. No. 3,807,982 to Claassen and Canonaco disclose fluid permeable conveyor rolls especially suitable for conveying either flat or shaped glass sheets while hot through a glass sheet chilling station. The rolls of these patents have a rigid center shaft, a pair of hubs, additional peripheral shafts interconnecting the peripheral portions of the hubs, and means for adjusting the angular position of at least one of the hubs with respect to the other hub so that the peripheral shafts extend at an angle to the rigid center shaft from hub to hub, thus defining a series of lines that intersect a curvilinear plane conforming to the shape of conveyed bent glass sheets and provide lines of support that move obliquely of the path of glass movement. Each peripheral shaft is preferably of a material rigid enough to support the glass, yet flexible enough to bend in response to relative hub rotation, such as metal wire. To protect glass sheets from direct contact against the metal wire, a material that does not mar hot glass is interposed between the peripheral shafts and the supported glass. The space between adjacent conveyor rolls is left open to allow free flow of tempering medium toward the supported bottom glass sheet surface.
According to the Claassen and Canonaco patent, a sleeve of a permeable material is provided around the discontinuous surface of the peripheral shafts or wires to protect against direct contact between the peripheral shafts of each flexible roll and the glass. The permeability of the sleeve permits additional flow of tempering medium between the rigid center shaft and the flexible peripheral shafts and also between adjacent of said peripheral shafts en route to the supported glass surface.
The Canonaco patent provides beads of a material harmless to glass along the length of each peripheral shaft to prevent the glass sheets from making direct contact with the peripheral shafts. The beads are so small that space is provided between adjacent peripheral shafts and between the rigid center shaft and the peripheral shafts to permit flow of tempering medium through said conveyor roll toward the bottom surface of the conveyed glass sheets.